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# trig question watch

1. find values of theta in interval 0< (or qual toZ) theta < 360

cosi (theata +75) = 0

thanks!
2. you do inverse cos so

cos-1 (0) = ???? ( u get two ansers)

(To get the other answer you must either look on the cast diagram or the cosine curve.)

(theta + 75) = ?????(1) and ?????(2)

theta = ????(1) - 75 and ????(2) - 75

Keeping in mind the theta values must lie in the range 0 - 360
3. this is what i did: cosi 0 = 90 or 270

270- 75 = 195
90-75 = 15

but the markscheme (setB paper 1) says: theatra = 225 or 345
4. Well if you quote the question correctly the markscheme is wrong.

cos(225 + 75 ) = cos(300) which is not 0.
5. the question must have said:

cosi (theata +75) =1/2 then or the mark scheme is wrong.

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